This invention relates to optical multiplex systems and methods.
Optical transducers are becoming more common, such as for detecting various functions in aircraft. Because of the large number of transducers that may be necessary in a system, it is desirable to multiplex them in order to reduce the number of cables and connections in the system.
Commonly, multiplexing is achieved in one of two different ways. In time-division multiplex systems, each transducer provides an output at a different time and a de-multiplexer is used to provide outputs in respect of each transducer by interrogating each transducer in turn when that transducer is providing its output. Time-division multiplex systems are, however, difficult to use in optical systems because of the difficulty of triggering the transducers to provide an output only at specified times.
In optical frequency--or wavelength-division multiplex systems, the transducers are responsive only to radiation within a specific band of wavelengths and each transducer is responsive to different bands. Such systems include several radiation sources that each supply the radiation to respective ones of the transducers, and several receivers responsive to radiation in the respective narrow bands so that the output of each transducer can be continuously monitored. While wavelength-division multiplex systems can function satisfactorily, they can be complex because of the need to provide individual radiation sources associated with each transducer. Furthermore, failure of one source may go undetected since it is indistinguishable from a low output of its associated transducer.